WATERWAYS FORMATION: BRACHIOPOD COMMUNITIES AND CHANGING MORPHOLOGY ACROSS DIFFERENT ENVIRONMENTS

The relationship between morphology and environment is well established for many species; however, examination of similar patterns at higher taxonomic levels may provide a richer understanding of evolutionary ecology. The Devonian Waterways Formation in Alberta, Canada provides a useful setting to explore the potential relationships between environment and morphology within higher taxonomic groups. We use simple morphological measurements to compare brachiopod taxa from three stratigraphic members within the Waterways Formation. Within these members, brachiopods are abundant and well-preserved.

The two lower members, Firebag and Calumet, have a relatively greater siliciclastic content than the higher Moberly Member, which is mostly wacke- and pack-stones. Brachiopods of several higher taxonomic morpho-groupings (biconvex atrypides/orthides, concavo-convex strophomenides/productides, and alate spiriferides) were sampled from 7 beds through the Firebag, Calumet, and Moberly. Only specimens with no evidence of damage or deformation were examined and digitized in dorsal and lateral views. Length, width, height, dorsal valve height, and position of both maximum width and height along the length axis, were measured on each specimen.

Preliminary results suggest Calumet brachiopods were larger, and on average, the more rounded morpho-groups displayed greater valve inequality (either dorsally or ventrally inflated). Moberly atrypides tended to be rounder (both in terms of valve inflation/equity and basic outline) compared to atrypides in the Firebag and Calumet (t-test, p < 0.05). Schizophoria, similar to the pattern in atrypides, tends to exhibit a more rounded outline (rather than shield-shaped) higher in the section. Additionally, both atrypides and spiriferides became more equi-valved in the Moberly than in stratigraphically lower communities. These atrypide results are similar to previous work using more complex morphometrics on the same samples, suggesting that morphological trends are apparent at high taxonomic levels and that changes in different taxonomic groups can be convergent. Furthermore, these preliminary findings hint that relatively simple measures of broad brachiopod shape may be successful in capturing changes across different environments.